MIAMI-DADE, FL (CNN/Gray News) – Some bikers taking a stand against gun violence got in trouble with the law in South Florida.

Police said at least 18 people have been arrested since Friday during the “Wheels Up, Guns Down” event.

Some riders were seen doing dangerous stunts on motorcycles and ATVs, including popping wheelies. Others were speeding or cutting off drivers.

Police said they also confiscated nearly three dozen dirt bikes and ATVs.

The annual event usually takes place over the Martin Luther King Jr. Day weekend to protest gun violence, but police said at least two of those arrested were actually armed – they now face weapons-related charges.

All-terrain vehicles are illegal to ride on roadways, and police said the protest endangers drivers because of the dangerous stunts being performed, WTSP reports.

A man was killed at the event two years ago when a bike slammed into a car in Miami, WTVT reports.